A diamond composed of 100% pure carbon without any impurities is incredibly rare. Almost all diamonds contain some degree of colour impurity, known as inclusions, typically caused by long-drawn-out traces of nitrogen, boron or hydrogen which are present while the gems are forming deep within the earth.
These natural birthmarks are often not visible to the naked eye, but can affect the transparency or brilliance of a diamond.
A 6-category scale is used to grade diamonds based on their clarity:
The Clarity Scale
No inclusions or blemishes visible under 10x magnification. The stone is completely clear.
No inclusions visible under 10x magnification. There are however very small blemishes, noticeable to only experts.
Incredibly slight inclusions only noticeable to experts under a 10x microscope.
Minor inclusions that are observed with effort under 10x magnification.
Inclusions that are visible under 10x magnification.
Inclusions that are obvious under 10x magnification and potentially visible to the naked eye.
Clarity-enhanced diamonds are stones that have had their inclusions removed or hidden through a specific procedure. These kinds of diamonds are an excellent option if you are looking for a larger carat stone at a more affordable price.
Special care needs to be taken with these kind of diamonds. Immense heat or pressure can loosen the enhancement, so if you are getting your jewellery cleaned or modified it is important to inform the jeweller that it is a clarity-enhanced stone.
There are two main procedures for refining a diamond's clarity:
This process is used specifically for diamonds with small and dark inclusions. Firstly, a laser is used to drill a path (thinner than a strand of hair) into the interior of the diamond. After the path is made, the laser will either burn the inclusion away, or a special mix of chemicals is applied to dissolve the inclusion.
Fracture filling removes the visibility of white-coloured fractures, known as feathers, from a diamond. A glass-like material is poured into the feather to make it less noticeable. Good fracture filling is incredibly delicate, making it visible only to qualified diamond graders.